Menaquinone 9

Menaquinone 9 (MK-9) is a vitamin K2 analog found in various bacteria, including Escherichia coli^{[1, 2]}. MK-9 functions as a blood clotting factor and a functional electron-transfer component in nitrate reductase^[3]. MK-9 is typically obtained from animal tissues or fermented dairy products such as cheese^[4]. High dietary intake of MK-7, MK-8, and MK-9 may help prevent coronary heart disease^[5]. Although dietary MK-9 is a precursor to MK-4 in bone tissue, dietary MK-9 supplementation does not affect bone tissue quality or bone mineral density^[6].

References:
[1] Crāciun A M, Groenen-van Dooren M, Thijssen H H W, et al. Induction of prothrombin synthesis by K-vitamins compared in vitamin K-deficient and in brodifacoum-treated rats[J]. Biochimica et Biophysica Acta (BBA)-General Subjects, 1998, 1380(1): 75-81.
[2] Koehn J T, Crick D C, Crans D C. Synthesis and characterization of partially and fully saturated menaquinone derivatives[J]. ACS omega, 2018, 3(11): 14889-14901.
[3] Brito F, DeMoss J A, Dubourdieu M. Isolation and identification of menaquinone-9 from purified nitrate reductase of Escherichia coli[J]. Journal of bacteriology, 1995, 177(13): 3728-3735.
[4] Vermeer C, Raes J, Van’t Hoofd C, et al. Menaquinone content of cheese[J]. Nutrients, 2018, 10(4): 446.
[5] Gast G C M, de Roos N M, Sluijs I, et al. A high menaquinone intake reduces the incidence of coronary heart disease[J]. Nutrition, Metabolism and Cardiovascular Diseases, 2009, 19(7): 504-510.
[6] Liu M, Liu C, Cevallos N, et al. Dietary Menaquinone-9 Supplementation Does Not Influence Bone Tissue Quality or Bone Mineral Density in Mice[J]. bioRxiv, 2025.

Menaquinone 9（MK-9）是一种维生素K2类似物，已在各种细菌中发现，包括大肠杆菌^{[1, 2]}。Menaquinone 9能够作为血栓形成剂和硝酸还原酶中的功能性电子传递成分^[3]。Menaquinone 9通常来源于动物组织或者发酵的乳制品，例如奶酪^[4]。大量摄入膳食MK-7，MK-8和MK-9，能够预防冠心病^[5]。尽管膳食MK-9是骨骼中MK-4的膳食前体，但膳食MK-9补充剂不影响骨组织质量或骨矿物质密度^[6]。